Flow valves that serve to regulate the flow of fluids in environments that are subjected to extreme temperature fluctuations are known. Generally, a change in temperature to the environment of the container holding the fluid causes a change in temperature of the fluid contained within. Additionally, this change in temperature causes either an increase, or a decrease in pressure. Generally, an increase in temperature causes an increase in pressure, and a decrease in temperature causes a decrease in pressure. When you apply these changes in pressure to an actuator the performance of the actuator also changes. Inside a typical actuator resides a piston wherein applying a high pressure flow on that piston will instigate a greater force. The greater force causes the actuator to move with greater velocity. Conversely, if temperature is low, then pressure is low. The low pressure causes a decrease in force exerted on the piston. This decrease in force causes the piston to move slower. It is desirable to control flow of gas into the actuator so that when temperature and pressure are low, the orifice that regulates the flow of the fluid is larger, thereby allowing gas to flow quickly into the actuator. Conversely, when the temperature and pressure are high the aforementioned orifice of the valve should be smaller, so that the gas flow into the actuator is restricted.
In view of the above, it is essential for many applications to keep the flow rate of fluid constant while temperature fluctuates between hot and cold extremes. One such application, requiring a constant flow rate during temperature fluctuations, is in the field of aeronautics.
Devices that provide a stable fluid flow are known. One such device is the Fluid Dispenser With Stabilized Fluid Flow described in U.S. Pat. No. 6,413,238. The device provides a fluid dispenser and method of operation. The device includes a feedback system which allows the device to respond in a timely and measured manner to changes in the dispensing flow rate of fluid from the device. The device has a fluid reservoir and an outlet which optionally may have a flow or pressure resistance unit incorporated, into the outlet, and an electric gas generation module or reversible pump which provides gas pressure to dispense the fluid from the reservoir. The device also has a sensor for detecting and measuring internal or external operating parameter indicative of flow rate of the fluid being dispensed. Feedback from the sensor is used by a controller to control electric current to the gas generation module, with the current being adjusted by the controller to adjust the amount of gas produced in a manner which will prevent the flow rate of the dispensed fluid from exceeding desired maximum or minimum limits.
While the aforementioned device regulates the flow of a fluid and adjusts for changes in pressure, the device is extremely complex and requires many electronic components including sensors and detection units. Additionally, such a device is expensive to manufacture.
An additional device for regulating a fluid is disclosed in the Blue Flame Gas Smooth Top Range of U.S. Pat. No. 3,870,457. The thermal fuel valve is used with an electric igniter in a gas range appliance to control gas flow while the igniter provides automatic gas ignition at a burner. The electric igniter is positioned next to the burner and an internal electric heater in the thermal fuel valve enclosure is positioned to heat a thermally responsive heat warpable actuator that moves the poppet to open the valve when the devices are connected for series electric energization. The thermal fuel valve will open and allow gas to flow to the burner only when the electric igniter has been energized. Furthermore, the valve is calibrated to open only when the igniter is near or at a temperature suitable for igniting the gaseous fuel. Since the force required to be exerted by the actuator to move the poppet from its seat is dependent on the gas pressure in the valve, such calibration normally would take into consideration the normal gas pressure.
While the aforementioned device either opens or closes depending on temperature, it does not serve to regulate the flow rate of fluid constant while temperature fluctuates between hot and cold extremes. The device merely allows for gas to flow provided the temperature is at an appropriate level.
What is needed in the art is a gas valve that maintains a defined flow rate across a temperature range even though the upstream pressure fluctuates with temperature.
Furthermore, what is needed in the art is a gas valve that maintains a defined flow rate across a temperature range even though the upstream pressure fluctuates with temperature, wherein the gas valve is substantially mechanical and does not require additional temperature monitoring or controlling devices.